Coherent phase locking of High-T-c YBa2Cu3Oy, Josephson junctions

We measured I-V curves and noise characteristics of high-T-c YBa2Cu3Oy step -edge Josephson junctions and serial junction arrays under microwave irradi ation. The junctions were fabricated on step-edge MgO(100) substrates with low step angles (similar to 30 degrees) The junction array shows the resist ively shunted junction (RSJ) behavior for at least 50 junctions and reveals a coherent phase locking under microwave irradiation. The variation of I-c was 16% for a 150-junctions array distributed along the step-edge line of 1.5 mm in width. The voltage noise, S-v, of the serial junction array scale s as the number of junctions, N. The value of S-IR, (S-IR = \(deltaI(c)/I-c )parallel to(deltaR/R)\), for a single and 50-junctions obtained from the f luctuation measurement is consistent with the result derived from IcRn prop ortional to (J(c))(q), with q = 0.5.